A light source for illumination used in a projection type image display device such as a liquid crystal projector is used with a reflector in order to efficiently make a light flux emitted from a lamp be incident on a limited plane.
As background technology in this technical field, there is JP 2008-242156 A (Patent Document 1). Patent Document 1 intends to provide a compact light source device with little light loss and a projector incorporating the light source device, in which a reflector is constituted by first, second, third, and fourth reflector portions which are parts of a spheroid. A first focal point of each of the reflector portions is disposed at a light emission point of a light emission tube, and a second focal point of each of the reflector portions is disposed on the side of each of the reflector portions with respect to a system optical axis. Thereby, it is disclosed that the light reflected by each of the reflector portions can be prevented from being blocked by a light emission tube or a sub-reflection mirror around the system optical axis.